The present invention relates generally to phased array antennas and, more particularly, to conformal phased array antennas and associated methods of repair.
Antennas are widely utilized in order to transmit and receive a variety of signals. For example, antennas are prevalent in radio frequency (RF) communication systems. One common type of antenna utilized for high data rate communications with moving platforms, such as aircraft or the like, is a phased array antenna. Phased array antennas generally include a number of identical radiating elements. Each element may include a phase shifter and/or a time delay circuit. In addition, each element may include an amplifier. By adjusting the phase shift of each element, the beam transmitted and/or received by the phased array antenna may be formed electronically and steered without physical movement of the antenna aperture.
One conventional phased array antenna is depicted in FIG. 1. As shown, the phased array antenna 100 includes a number of RF modules 102. Each RF module generally includes a phase shifter and an amplifier. This conventional phased array antenna also includes a shim element 104 defining a number of openings 106 arranged in the predefined pattern or an array. The RF modules are therefore mounted within respective openings defined by the shim element such that the RF modules are also disposed in the predefined pattern. The phased array antenna also includes a multilayer wiring board 108 having a number of wires, conductive traces or the like. The shim element is disposed upon the multilayer wiring board such that the RF modules make contact with the multilayer wiring board and, in particular, with respective wires or conductive traces carried by the multilayer wiring board. Although not illustrated, the multilayer wiring board is also generally connected to a power supply, ground and a clock, as well as various address and data lines. The multilayer wiring board therefore supplies power, ground and clock signals to the RF modules, while permitting data to be transmitted to and from the RF modules.
The phased array antenna 100 of FIG. 1 also includes an aperture honeycomb structure 110 having a pair of opposed planar surfaces and defining a plurality of passages 112 extending between the opposed planar surfaces. The aperture honeycomb structure defines the passages in the same configuration as the openings defined by the shim element 104. As such, the RF modules 102 mounted within the openings 106 defined by the shim element are aligned with respective passages defined by the aperture honeycomb structure. The aperture honeycomb structure may be formed of various materials, but is typically formed of a metal, such as aluminum, a conductively coated or conductively plated plastic, a metal matrix composite or a conductively coated composite material. Dielectric inserts 114 are disposed within the passages defined by the aperture honeycomb structure. These dielectric inserts facilitate the propagation of signals through the passages such that the respective RF module may transmit and/or receive signals via the dielectric loaded passages defined by the aperture honeycomb structure. The phased array antenna also includes the wide angle impedance match (WAIM) layer 116 that overlies the outer surface of the aperture honeycomb structure. The WAIM layer is constructed from a number of dielectric layers that mitigate the impact of mutual coupling effects on aperture performance at relatively high scan angles. The phased array antenna further includes an enclosure 118 within which the other components of the phased array antenna are disposed. The enclosure protects and maintains the alignment of these other components and facilitates the mounting of the phased array antenna to a structure, such as to an airframe or the skin of an aircraft, by permitting the enclosure to be mechanically connected to the structure. While one conventional phased array antenna is depicted in FIG. 1 and described above, another phased array antenna is described by U.S. Pat. No. 5,276,455 to George W. Fitzsimmons, et al., the contents of which are incorporated herein in their entirety.
Phased array antennas are generally mounted proximate the exterior surface or skin of a structure. In order to protect the phased array antenna and to facilitate the relatively smooth flow of air thereabout, conventional phased array antennas are typically housed within an aerodynamic fairing, a radome or the like. Various types of aerodynamic fairings and radomes, such as blister or bubble radomes, can be utilized to protect the phased array antenna and to permit the relatively free flow of air therearound. Housing the phased array antenna within an aerodynamic fairing, a radome or the like is particularly advantageous in those instances in which the phased array antenna does not conformally blend into the surrounding structure.
As illustrated in FIG. 1 and as described above, the outer surface of a conventional phased array antenna is planar. In many applications, however, the phased array antenna is mounted to a structure that is not planar, but is curved or has some other contour. In these instances, a conventional phased array antenna cannot generally be mounted conformal to or flush with the surrounding surface of the structure. By housing the phased array antenna within an aerodynamic fairing, a radome or the like, however, the phased array antenna is protected.
While aerodynamic fairings, radomes and the like provide a number of advantages, these structures also create several disadvantages. In particular, aerodynamic fairings, radomes or the like increase the costs of the resulting antenna assembly. In addition, aerodynamic fairings, radomes or the like may adversely affect the RF performance of the phased array antenna. In conjunction with those phased array antennas mounted upon moving structures, such as aircraft, an aerodynamic fairing, radome or the like adds weight and imposes an aerodynamic drag penalty which, in turn, will increase fuel consumption among other things. Further, an aerodynamic fairing, a radome or the like will also disadvantageously increase the radar cross section of the structure, such as the aircraft, upon which the phased array antenna is mounted.
A phased array antenna and associated method of repairing a phased array antenna are provided to address the aforementioned and other disadvantages associated with conventional phased array antennas. In this regard, a phased array antenna of the present invention may be designed to conform with the surface or skin of the structure to which the phased array antenna is mounted. As such, the phased array antenna of the present invention need not be housed within an aerodynamic fairing, a radome or the like. Moreover, by designing the phased array antenna to have individual subassemblies or line replaceable units, the phased array antenna can be readily repaired without completely removing or deconstructing the phased array antenna.
According to one aspect of the present invention, the phased array antenna includes a planar antenna subassembly including an array of RF modules disposed in a reference plane. The planar antenna subassembly also generally includes a planar aperture honeycomb structure. The planar aperture honeycomb structure defines a number of passages in communication with respective RF modules. The phased array antenna of this aspect of the present invention also includes a contoured waveguide subassembly including a contoured aperture honeycomb structure. The contoured aperture honeycomb structure also defines a number of passages extending between the opposed first and second surfaces. The contoured aperture honeycomb structure is disposed with respect to the planar antenna subassembly such that each RF module is in communication with a respective passage of the contoured aperture honeycomb structure. In this regard, the contoured aperture honeycomb structure is generally disposed with respect to the planar aperture honeycomb structure such that respective passages of the contoured and planar aperture honeycomb structures are aligned, thereby placing each RF module in communication with a respective passage of the contoured aperture honeycomb structure.
The contoured aperture honeycomb structure is disposed with respect to the planar antenna subassembly including, for example, the planar aperture honeycomb structure, such that the first surface of the contoured aperture honeycomb structure faces the planar antenna subassembly and the second surface of the contoured aperture honeycomb structure faces away from the planar antenna subassembly. According to the present invention, the second surface of the contoured aperture honeycomb structure is contoured such that at least portions of the second surface are at an oblique angle with respect to the reference plane in which the RF modules are disposed. In other words, at least portions of the second surface are at an oblique angle with respect to a planar surface of the planar aperture honeycomb structure. As such, the second surface of the contoured aperture honeycomb structure may be contoured so as to match or blend into the contour of the surface or skin of the structure to which the phased array antenna is mounted.
The contoured waveguide subassembly may also include a WAIM radome layer. The WAIM radome layer overlies the second surface of the contoured aperture honeycomb structure. In addition, the WAIM radome layer may have the same contoured shape as the second surface of the contoured aperture honeycomb structure, thereby facilitating the conformance of the phased array antenna to the shape of the structure to which the phased array antenna is mounted.
As a result of the contour defined by the second surface of the contoured aperture honeycomb structure, at least some of the passages have different lengths as measured between the opposed first and second surfaces. The contoured waveguide subassembly may also include a number of dielectric inserts disposed within respective passages of the contoured aperture honeycomb structure. Each dielectric insert extends between opposed first and second ends. The dielectric inserts are positioned within the respective passages such that the second ends of the dielectric inserts are proximate the second surface of the contoured aperture honeycomb structure. The second end of at least one dielectric insert is also advantageously contoured to match the contour of that portion of the second surface of the contoured aperture honeycomb structure proximate thereto. As such, the combination of the second surface of the contoured aperture honeycomb structure and the second ends of the dielectric inserts may define a smoothly curved or contoured surface which matches or blends into the contour of the structure to which the phased array antenna is mounted, thereby obviating the need for a fairing, a radome or the like and avoiding the disadvantages associated with the use of a fairing, a radome or the like.
According to another aspect of the present invention, a method of repairing a conformal phased array antenna having a planar antenna subassembly and a contoured waveguide subassembly is provided. According to this method, one of the subassemblies, that is, either the planar antenna subassembly or the contoured waveguide subassembly, is removed while the other subassembly remains installed. For example, the contoured waveguide subassembly may be removed while the planar antenna subassembly remains installed. After removing one of the subassemblies, a subassembly of the same type as the removed subassembly is installed by aligning the subassembly that is being installed with the other subassembly that has remained in place to permit communication therebetween, such as communication between the RF modules of the planar antenna subassembly and the passages defined by the contoured aperture honeycomb structure. The subassembly that is installed may be a repaired version of the same subassembly that was removed or may be a replacement therefor. In either instance, the method of this aspect of the present invention facilitates the efficient repair of the phased array antenna by permitting the phased array antenna to be separated into subassemblies or line replaceable units that may be individually removed and reinstalled without having to similarly remove and reinstall the other subassembly.